The present invention relates to a new strain of Streptomyces isolated from the soil of geranium (Pelargonium graveolens) at Central Institute of Medicinal and Aeromatic Plants (CIMAP), Lucknow, Indiaxe2x80x94the newly isolated strain Streptomyces CIMAP-A1 is capable of inhibiting the growth of a wide range of phytopathogenic fungi and has been found to be highly effective in protecting rose-scented geranium from anthracnose disease caused by Colletotrichum acutatum and opium poppy from damping-off caused by Pythium dissotocum. The said novel strain of Streptomyces has been isolated from a soil at CIMAP, where field experiments in respect of the plant Pelargonium graveolens were conducted.
Fungal phytopathogenes cause considerable damage to the medicinal and aromatic plants. These pathogens produce various kinds of diseases whose occurrence in severe form may either kill emerging seedlings or reduce plant growth and adversely effect crop yield. Various phytopathogenic fungi including Rhizoctonia, Sclerotinia, Pythium, Fusarium, Curvularia, Alternaria, Collectotrichum and Thielavia cause different types of diseases on medicinal and aromatic plants such as stem rot and twig blight (Sclerotinia sclerotiorum) on periwinkle, Egyption henbane, and ammi majus; leaf blight (Curvularia andropogonis); lethal yellowing (Pythium aphanidermatum) and collar rot (Fusarium moniliforme) on Java citronella; damping-off (Pythium dissotocum), collar rot (Rhizoctonia solani) and leaf blight (Alternaria alternata) opium poppy, stolon and root rot (Thielavia basicola) on mints and anthracnose disease Colletotrichum acutatum on geranium. (Alam et al 1983, Indian Phytopath. 367: 480-483, ibid 1992 Plant 43:10578-1061; ibid 1996 Indian Phytopath. 49:94-97; Sattar et al 1993, Indian J. Plant Pathol 10: 10-11; ibid 1999, Indian J. Plant Pathol 17:74-76).
Chemical pesticides are commonly used to protect plants from the fungal infections but their intensive and indiscriminate uses pose many serious problems such as development of resistant strains of the pathogen, build up of harmful residues in the plant parts, non-target effect on beneficial microflora and environmental pollution. Thus, to avoid such problems. attention has been focused to use microorganisms such as fungi, bacteria and actinomycetes as biocontrol agents to minimize infection caused by plant pathogens.
Streptomyces spp. are commonly distributed in the soil rhizosphere and phyllosphere by which they produce strong antagonistic effect on the fungal phytopathogens and protect plants from the attack of the pathogens (Broadbent et al 1971, Aust. J. Biol. Sci 24: 925-944, Lahdenpera 1987, Acta Horticulture 216: 85-92, El-Abyad et al 1993. Plant and Soil, 149 185-195). Streptomyces griseoviridis isolated from Finnish sphagnum peat produce strong antagonistic effect on the growth of Fusarium culmorum, Pythium debaryanum and Rhizoctonia solani and its spraying reduce the damage caused by them (Tahvonen, 1985, Vaxskyddsnotiser 49 86-90, White el al. 1998, In Brighton Crop Protection Conference on Pests and Diseases vol 1: 221-226). A direct evidence that the antibiotic geldamycin produced by Streptomyces hygroscopius var. geldanus suppressed the growth of Rhizoctonia solani, thus controlled Rhizoctonia root rot of pea (Rothrock and Gottlieb, 1984, Can. J. Microbiol 30: 1440-1447). Several Streptomyces cultures have been isolated from the soil of CIMAP experimental fields at Lucknow and they have been maintained in our culture collection. One of the isolates of Streptomyces i.e. Streptomyces CIMAP-A1 shows strong antagonistic activities against the wide range of fungal phytopathogens in vitro. One of the most recent and taxonomic studies of Streptomyces was carried out in the International Streptomyces Project (I.S.P) where more than 400 type strains were examined independently by Standardized procedure (Shirling E B and Gottlieb D. 1968, International Journal of Systematic Bacteriology, 18: 69-186, 279-31; Ibid. 1961 International Journal of Systematic Bacteriology 22: 265-394). Streptomyces species were assigned to seven color series i.e. blue, green, gray, red, violet, white and yellow (Pridham and Tesener, 1974, Family VII Streptomyectaceae Waksman and Henriei, 1943. IN Bergey""s Mannual of Determinative Bacteriology, 8th edn., ed Buchman, R E and Cibbon, N. E. pp.747-845 Baltimore; Willams and Wilkins). Subsequently, the color series were extended to accommodate additional colors. The distinctive morphology of the sporing structures have been widely used in the characterization of Streptomyces species. The spore chain morphology determined by light microscopy and spore surface ornament determined by electronic microscopy have been considered important in many classifications. (Etlinger et al 1958, Archive fur Mikrobiologie 31,326-358, Waksman S. A. 1961, The Actinomycestes Vol.2. Classification, Identification and Description of General and Species, Baltimore: Williams and Willins, Hutter, R. 1967. Systematik de Steptomyceten. Basel and New York S Karger).
Streptomyces spp. are morphologically characterized by the production of highly branched substrate mycelium (rarely bearing spores) that further form a network of white aerial hyphae bearing spores in chain at the tip of sporogenous filament (Kustner, E, 1961; International Bulletin of Bacteriological Nomenclature and Taxonomy 11, 91-98).
The main object of the present invention relates to a novel strain of Streptomyces spp. (CIMAP A1) having potential antifungal activities and capable of reducing infection by fungal pathogens.
An another object of the invention is to use the newly isolated strain of Streptomyces spp. (CIMAP A1) for the control of different diseases like damping off disease of opium poppy and anthracnose disease of rose scented geranium by application in a suitable medium.
The invention provides a novel Streptomyces sp. capable of inhibiting the growth of a wide range of phytopathogenic fungi.
The strain deposited at the American Type Culture Collection (ATCC), Manassas, Va. on Mar. 12, 2002, and assigned to Accession Number PTA-4131.
The present invention pertains to the isolation of a number of actinomycetes from the soil and identification of a new Streptomyces strain referred to as Streptomyces CIMAP-A1. The stain is deposited at American Type Culture Collection (ATCC), Manassas, Va, on Mar. 12, 2002, and assigned to Accession Number PTA-4131. This strain is shown to exhibit strong antagonism towards a wide range of fungal phytopathogens that cause various kinds of diseases such as damping-off, root rot, stem rot, collar rot, twig blight, lethal yellowing, leaf blight and anthracnose as shown in Table 1. As such, this Streptomyces strain is suitable as biocontrol agent that can be used to protect plants against infection by these phytopathogens. Thus, Streptomyces CIMAP-A1 is useful in methods for reducing the susceptibility of plant to fungi infection.
Accordingly, the novel strain of Streptomyces, Streptomyces CIMAP-A1, has been found to inhibit growth of Streptomyces sp. and Botrytis cincrea by more than 90%, of Sclerotinia sclerotiorum by more than 85%, of Curvularia spp by more than 80%, of Alternaria spp by more than 65% of Corynespora cassiicola by more than 64% of Thielavia basicola by more than 54% of Rhizoctonia solani by more than 20% of Pythium spp by more than 20% and of Fusarium spp by more than 25% in vitro. The invention further provides information on the characterization of the strain Streptomyces CIMAP-A1 which initially produce smooth and dull white colonies on PDA which later form discrete lichnoid colonies. In the later stages of growth, it produces a weft of aerial mycelium and turn into dark brown in color and the aerial mycelium at maturity form chain of spiral spores called orthrospores. Since species delineation within the genus Streptomyces is difficult and it requires a large amount of chemotaxonomic and molecular tests, the applicants designate the strain as Streptomyces CIMAP-A1.
Accordingly, the invention provides a biologically pure culture of Streptomyces sp., CIMAP A1 strain bearing accession No. ATCC PTA-4131 and capable of inhibiting the growth of phytopathogenic fungi.
Another embodiment of the invention provides a new stain of Streptomyces sp., called CIMAP A1 isolated from the soil of geranium (Pelargonium graveolens) planted in the experimental fields of CIMAP and having the accession No. ATCC PTA-4131 and capable of inhibiting the growth of phytopathogenic fungi.
Still another embodiment of the invention provides a novel strain having the following characteristics:
a) producing smooth, dull white colonies on Poison Disk Assay (PDA) which later forms discrete and lichonoid colonies,
b) in late stages of growth, the present strain produces white aerial mycelium which later turn into dark brown in color,
c) aerial mycelium at maturity form chain of spores, and
d) exhibiting unique fingerprint pattern as shown in FIG. 3.
Still another embodiment of the present invention provides a strain Streptomyces CIMAP-A1 having highly effective growth inhibiting properties against Sclerotinia sclerotiorum by 90%, Curvularia andropogonis by 85%, Alternaria phragmospora by 66% and Colletotrichun acutatum by 60%.
Yet another embodiment of the present invention provides a culture (CIMAP-A1) which exhibits photopathogenic activity against the Phytopathogenic species selected from the group comprising Rhizoctonia, Sclerotinia, Pythium, Fusarium, Curvularia, Alternaria, Collectotrichum and Thielavia.
One more embodiment of the present invention provides a method for evaluating antifungal activity of CIMAP-A1 vitro against wide range of phytopathagenic fungi of medicinal and aromatic plants.